CB1 and CB2 receptors, two subtypes of the cannabinoid receptor, both belong to the G-protein-coupled receptor (GPCR) superfamily.
The CB1 receptor is predominantly expressed in brain to mediate inhibition of transmitter release. It affects many neurological and psychological phenomena, such as mood, appetite, emesis control, memory, spatial coordination muscle tone, and analgesia. See, e.g., Goutopoulos et al., Pharmacol Ther (2002) 95:103.
The CB2 receptor is primarily expressed in immune cells to modulate immune response. Activation of the CB2 receptor has been shown to have analgesic effects in inflammatory models involved in neurodegeneration diseases, and play a role in the maintenance of bone density and progression of atherosclerotic lesions. See, e.g., Malan et al., Pain (2001) 93:239; Benito et al., J Neurosci (2003) 23:11136; Ibrahim et al., Proc Natl Acad Sci USA (2003) 100:10529; Idris et al., Nat Med (2005) 11:774; and Steffens et al., Nature (2005) 434:782.